GENEVA: The UN on Tuesday urged the Saudi-led coalition to end a blockade of Yemen which has halted the flow of humanitarian supplies into the country, further threatening some seven million people facing famine-like conditions.

"If these channels, these lifelines, are not kept open it is catastrophic for people who are already in... the world's worst humanitarian crisis," Jens Laerke, a spokesman for the United Nations humanitarian office (OCHA), told reporters in Geneva.

Relief supplies into Yemen have been blocked since the coalition sealed off the country's borders following a missile attack last weekend by Yemen's Houthi rebels that was intercepted near the Riyadh airport.

Humanitarian flights into Yemen have been on hold since Monday.

The coalition has also asked the UN to clear ships from the port of Hodeidah, which "is the backbone of the humanitarian operations in Yemen," OCHA said in a statement.

"Fuel, food and medicine imports must continue to enter the country," Laerke said. "This is an access problem of colossal dimensions".

In the immediate aftermath of the blockade, fuel prices have jumped by up to 60 per cent and cooking gas prices have doubled, he added.

OCHA is in talks with the coalition to restore access as soon as possible, Laerke said.

The Saudi-led Arab military coalition intervened in Yemen in March 2015 to support President Abedrabbo Mansour Hadi after the Houthis forced him into exile.

Last month, the United Nations put the coalition on its blacklist for killing and maiming 683 children during the conflict last year and for carrying out 38 verified attacks on schools and hospitals.

In updated figures, the UN's rights office said 5,295 civilians had been killed in Yemen since the coalition offensive began, and 8,873 have been injured.

But those figures represent only verified casualties by UN staffers, the rights office said, adding that "the actual numbers are likely to be far higher."